Unraveling a chemical-bond-driven root of topology in three-dimensional chiral crystals

Chirality generates striking quantum responses even in light-element materials. However, the real-space picture connecting crystal chirality to electronic topology through chemical bonding has remained elusive. Here we directly visualize the chiral bonding network responsible for multifold topological fermions by combining synchrotron X-ray diffraction and first-principles calculations on cubic chiral crystals, CoSi and FeSi. Based on observations of asymmetric valence electron distributions, together with bonding analyses, we develop a three-dimensional Su-Schrieffer-Heeger model, showing that inter-site hopping on this chiral network creates multifold fermions with doubled topological invariants. We demonstrate that topological features can be controlled through two distinct routes: crystalline chirality reversal and electron filling, the latter switching the bonding/antibonding character while maintaining crystal structure. This bonding-driven mechanism operates at eV-scale energies without requiring spin-orbit coupling, enabling robust topological phases at elevated temperatures. Moreover, this real-space framework naturally extends to other elementary excitations or metamaterials, enabling quantum functionalities through chirality engineering. Chiral crystals host topological fermions with robust quantum responses, yet a real-space picture linking chemical bonds and topology remains elusive. Here, the authors image the twisted electron distributions in CoSi and show that chirality-driven alternating bonds create topology without spin-orbit coupling, a route to designing chiral topology.